In the past conventional DC motors, commutation was effected by brushes riding on a segmented commutator so as to control the currents flowing through the armature winding sections of such past conventional DC motors. Of course, one of the disadvantageous or undesirable features attendent to the above discussed commutated DC motors is believed to be that wear of the brushes thereof necessitated frequent brush replacement. Other disadvantageous features of these past commutated DC motors are believed to be that sparking may have occurred between the brushes and segmented commutator thereof which not only may have effected RF interference but also may have limited the use of such commutated DC motors in some critical or particular environmental applications.
Various circuit and motor design schemes have been utilized in the past to develop various types of brushless DC motors, and one such scheme is shown in the David M. Erdman U.S. Pat. No. 4,005,347 issued Jan. 25, 1977 and U.S. Pat. No. 4,015,182 issued Mar. 29, 1977, each of which are incorporated herein by reference. In these patents, a brushless DC motor has a stator with a plurality of windings therein, a rotor having a plurality of constant magnetic polar regions, and means for sensing the relative position of the rotor polar regions with respect to the stator. Positive signals developed by the position sensing means were processed by circuitry for selectively energizing the windings of the motor.
In the present day clothes washing or laundry machines having a generally coaxially arranged agitator and a spin tub, the agitator is rotated with an oscillating movement, and the rotation of the spin tub is unidirectional at a speed appreciably greater than that of the agitator oscillation. Of course, many different transmission mechanism and drive schemes have been employed in the past to effect the aforementioned particular oscillation and unidirectional rotation of the agitator and spin tub; however, it is believed that a disadvantageous or undesirable feature of such past schemes was that they were too costly and/or too complicated not only from the viewpoint of manufacture but also from the viewpoint of power usage and maintenance by the consumer.